The present invention relates generally to hardcopy mechanisms, and more particularly to a subsystem of a hardcopy mechanism which changes state in response to movement of a service station member, and in the illustrated hardcopy printing mechanism embodiment, to a subsystem which adjusts printhead-to-media spacing in a printzone to accommodate different media (e.g. paper) thicknesses in response to movement of the service station member to provide high quality images on varying thickness of media.
Inkjet printing mechanisms use cartridges, often called xe2x80x9cpens,xe2x80x9d which shoot drops of liquid colorant, referred to generally herein as xe2x80x9cink,xe2x80x9d onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead is propelled back and forth across the page, shooting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett-Packard Company. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).
To clean and protect the printhead, typically a xe2x80x9cservice stationxe2x80x9d mechanism is mounted within the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which hermetically seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as xe2x80x9cspitting,xe2x80x9d with the waste ink being collected in a xe2x80x9cspittoonxe2x80x9d reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead. While earlier, more primitive servicing mechanisms were operated in response to printhead movement, the newer more advanced servicing mechanisms often employ a separate service station motor which operates to move the servicing members between their rest and servicing positions.
As a preliminary matter, there is a term of art used by inventors skilled in this art that will speed the reading if used herein, and it is xe2x80x9cpen-to-paper spacing,xe2x80x9d often abbreviated as xe2x80x9cPPSxe2x80x9d or xe2x80x9cPPS spacing.xe2x80x9d In the English language of the inventor, xe2x80x9cpen-to-paper spacingxe2x80x9d or xe2x80x9cPPSxe2x80x9d is easier to pronounce than the more technically explicit term xe2x80x9cmedia-to-printhead spacing,xe2x80x9d and for this reason the terms xe2x80x9cPPSxe2x80x9d or xe2x80x9cpen-to-paper spacingxe2x80x9d are used herein. During prototype testing and development, inventors use vast amounts of media, so the most plentiful and economical media, plain paper is used. Indeed, the short-hand term xe2x80x9cpen-to-paper spacingxe2x80x9d is a logical selection of terminology, although it must be understood that as used herein, this term encompasses all different types of media, unless specified otherwise in describing a particular type of media. Thus, xe2x80x9cpen-to-paper spacingxe2x80x9d (PPS) defines the spacing between the inkjet cartridge printhead and the printing surface of the media, which may be any type of media, such as plain paper, specialty paper, card-stock, fabric, transparencies, foils, mylar, etc.
Having dispensed with preliminary matters, the discussion of the problems encountered in this art in maintaining an accurate PPS now continues. For instance, there are variations in the thickness of the print media which affect the PPS spacing. For example, envelopes, poster board and fabric are typically thicker than plain paper or a transparency. Thicker media decreases the spacing from the printhead to the printing surface, and in the worst case, this reduced spacing could lead to contact of the printhead with the media, known as a xe2x80x9cprinthead crash,xe2x80x9d possibly damaging either the printhead or the image.
The earliest printing mechanisms used a constant printhead-to-media spacing, ignoring the media thickness and sacrificing print quality when thicker medias, such as envelopes or other media thicker than plain paper were printed upon. Unfortunately, one danger in ignoring printhead to paper spacing was the potential for suffering a printhead crash. To prevent printhead crashes, and subsequent printhead damage, as well as potentially ruining the print job, one prior solution provided a xe2x80x9cuser-switchxe2x80x9d for adjusting PPS spacing. These user operable PPS adjustments required users to turn a knob, or push a lever to increase the PPS for better print quality when printing on thicker media. Unfortunately, in these user switchable systems, most users either never understood the switch, or never knew the switch existed, and if they did, they rarely if ever used it, so they continually obtained disappointing outputs when switching between different thicknesses of media. Furthermore, even if consumers were aware of the user switchable PPS adjustment feature, and they did use it, the switch still requires an extra user intervention step in the printing process which would be desirable to eliminate to provide a more user-friendly product.
Normally to improve printing speed, known as xe2x80x9cthroughputxe2x80x9d measured in pages per minute, print quality is unfortunately sacrificed. Tests have shown that faster print speeds may be obtained, along with higher print quality, if the PPS spacing is reduced. One of the main stopping blocks to reducing PPS spacing lower than current levels is that envelopes, as well as other thicker print media, do not feed well through a nominal plain paper PPS spacing without smearing against the printheads. Thus, it would be desirable to have an automatic way to switch between two different printhead to platen separations, a large one for thicker media and small one for regular plain paper media, as well as transparencies, premium papers, and photo media.
Indeed, it would be desirable to provide more than two different PPS spacings to accommodate different types of specialty media. For example, plain papers often swell during printing as they soak up the liquid from the ink composition, a problem in the art often referred to as xe2x80x9ccocklexe2x80x9d where the media actually begins to buckle. Thus, for printing on plain papers the PPS spacing must be larger to avoid printhead crashes into upwardly bowed portions of the paper. In contrast, when printing upon various premium and photo medias, including transparencies, typically very little ink is absorbed into the media, so cockle is not a problem, allowing closer PPS spacings to be used. Closer PPS spacings are typically associated with yielding higher print quality, so in printing upon these specialty medias which are immune to cockle, it would be desirable to have a closer PPS spacing than when printing on plain paper. Indeed, as the various types of print media change, with different swelling characteristics and thicknesses, a variety of different spacings between the media support platen and the printhead may be desirable to accommodate these varying different thicknesses and cockle characteristics. Furthermore, as mentioned above it would be desirable to have this adjustment be accomplished without user intervention to provide a more robust, and easier to use printing mechanism, which continuously provides high print quality on a variety of different types of media.
One earlier media handling system tried to accommodate thicker envelopes, using a width sensor that detected media narrower than about 12 cm (4.5 in). Upon detecting this narrow media, a mechanical arm opened an inlet port on the media handling system to a much wider gap than normal to prevent ink smear on the envelope. Other earlier media handling systems lacked any ability to adjust the PPS spacing, other than adjustments made during initial assembly at the factory. One on-the-fly PPS adjustment system is disclosed in U.S. Pat. Nos. 5,838,338 and 6,102,509, currently assigned to the present assignee, the Hewlett-Packard Company. In this on-the-fly PPS adjustment system, the platen supporting the undersurface of the media in the printzone was lowered or raised to accommodate thicker or thinner media, respectively.
Given the ability of pen-to-paper spacing to affect print quality, one goal herein is to automatically adjust the PPS spacing to accommodate different thicknesses of media to maintain high print quality on all media thickness.
A broader goal herein is to provide a hardcopy mechanism with a subsystem which changes state in response to movement of a service station member.
According to one aspect, a method of operating on a hardcopy media with a hardcopy mechanism having a subsystem and a service station with a moveable member includes feeding the media to the hardcopy mechanism. The method also includes adjusting the subsystem from a first state to a second state using the moveable member. Finally thereafter, the method includes performing an operation on the media using the subsystem.
According to another aspect, a hardcopy mechanism is provided as including a subsystem which operates on hardcopy media in a first state or a second state. The hardcopy mechanism also includes a service station having a moveable member which cooperates with the subsystem to change from the first state to the second state.
According to a further aspect, a hardcopy printing mechanism for printing an image on media includes a media handling system which delivers media to a printzone, and a printhead which prints the image on the media when in the printzone. The printing mechanism also has a service station with a moveable member. The media handling system, the printhead, and the media when in the printzone, establish a spacing between the media and the printhead. The printing mechanism also has an adjustment member which adjusts the spacing in response to movement of the moveable member.
According to an additional aspect, a subsystem of a hardcopy mechanism, which has a service station with a moveable member, includes an activation member. The activation member adjusts the subsystem from a first state to a second state in response to motion of the moveable member. The subsystem also includes a locking mechanism which secures the subsystem in either the first state or the second state.
According to yet another aspect, a hardcopy mechanism includes a first subsystem which operates on hardcopy media in a first state or a second state. The hardcopy mechanism also has a service station with a moveable member which cooperates with the first subsystem to change between the first state and the second state.
According to an additional aspect, a hardcopy printing mechanism is provided for printing an image on media. The hardcopy mechanism has a media handling system which delivers the media to a printzone. A printhead prints the image on the media when in the printzone. The hardcopy mechanism has a service station with a moveable member. The media handling system, the printhead, and the media when in the printzone, establish a spacing between the media and the printhead. The hardcopy mechanism also has an adjustment member which adjusts the spacing in response to movement of the moveable member.
An overall goal herein is to provide a hardcopy mechanism, and a subsystem therefore, which changes state in response to movement of a service station member, and a method therefore.
A more specific goal herein is to provide a subsystem for the illustrated hardcopy printing mechanism embodiment which adjusts printhead-to-media spacing in a printzone to accommodate different media thicknesses in response to movement of a service station member to provide high quality images on varying thickness of media, and a method therefore, along with a hardcopy printing mechanism having such a subsystem.